Radiation plug for a particle accelerator beam tube



G. W. PARKER Oct. 14, 1969 RADIATION PLUG FOR A PARTICLE ACCELERATOR BEAM LUBE Filed Feb. 6, 1967 United States Patent US. Cl. 250-108 1 Claim ABSTRACT OF THE DISCLOSURE A water-filled shielding plug for use in a particle accelerator beam tube and adapted to be inserted into the beam tube from a branch tube comprising a metallic bellows closed at both ends and a wire for limiting longitudinal expansion of the bellows.

CONTRACTUAL ORIGIN OF THE INVENTION The invention described herein was made in the course of, or under, a contract with the United States Atomic Energy Commission.

BACKGROUND OF THE INVENTION This invention relates to a shielding plug and more particularly to a shielding plug for a particle accelerator. More sophisticated particle accelerators are constantly being developed to investigate the nature of the atom. In most of these machines more than one experiment may be conducted at a time by bending the beam into various parts and channeling each part to a separate experiment. There are innumerable instances where a particular section of the appartus has to be closed or the beam temporarily stopped while at the same time it would be widesirable to shut down the entire accelerator. The beam is then shuttered, and the plug of this invention isolates the apparatus room from the neutrons and bremssahlung that exists in the accelerator room.

Shielding plugs for use in a particle accelerator must be capable of stopping the high-energy neutrons and bremsstrahlung, withstanding intense radiation and operating in a high vacuum. A metallic billet of sutficient length for shielding, i.e., stopping the beam, could be used as a beam tube plug if a satisfactory method of inserting it into and removing it from the beam tube could be found. For various reasons, insertion sideways or lengthwise into the beam tube is undesirable. Insertion of the plug into the beam tube from a branch tube would be desirable, but since a billet is not flexible it is inapplicable for use with a branch tube.

SUMMARY OF THE INVENTION The plug of this invention meets all the above-mentioned requirements and comprises a metallic bellows closed at both ends, means connecting the ends of the bellows for limiting longitudinal expansion and a liquid beam barrier substantially filling the bellows. The liquid, which may be water, must be capable of Shielding, i.e., of stopping both high-energy neutrons and bremsstrahlung.

BRIEF DESCRIPTION OF THE DRAWING The plug of this invention may be better understood by reference to the single figure of the drawing which shows in cross section the plug within a particle accelerator beam tube.

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DESCRIPTION OF THE PREFERRED EMBODIMENT A plug 10 is formed of an elongated metallic bellows 11 consisting of alternating large-diameter segments 12 and small-diameter segments 13. The bellows 11 is closed at both ends by stoppers 14 and 15 and is substantially filled by a body 15a of liquid, such as water. Plug 10 as shown is in a shielding or beam-stopping position, that is, extending into beam tube 16 from branch tube 17, Which has a first part 17a extending at an acute angle from the beam tube and a second part 17b extending at right angles to the beam tube. The beam tube 16, branch tube 17 and plug 10 may be costructed from any suitable metal known to those skilled in the art, for instance, stainless steel.

Plug 10 is inserted into beam tube 16 by action of rod 18 which is attached to stopper 14 in such a manner that the plug may be inserted into or withdrawn from the beam tube by longitudinal movement of the rod which may be remotely controlled. Since a particle accelerator beam tube is operated under high vacuum, bellows 11 would expand longitudinally, but wire 19 attached to stoppers 14 and 15 prevents expansion beyond the length of the Wire. Since plug 10 is metallic, no expansion transverse to the longitudinal axis occurs, while at the same time the bellows configuration provides the necessary flexibility in order for the plug to be inserted at an angle from branch tube 17 into beam tube 16. The beam is restricted to a comparatively small cross-sectional area of beam tube 16; therefore, plug 10 need not be fitted snugly to the beam-tube walls. As will be noted from the drawing, bellows 11 is not closely fitted to beam tube 16; when plug 10 is filled with a body of liquid 15a and inserted into the beam tube, the beam tube is effectively sealed, because the high-energy neutrons and bremsstrahlung are stopped from proceeding by the liquid filled plug.

It will be understood that the invention is not to be limited to the details given herein but that it may be modified within the scope of the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In combination with a beam tube of a particle acclerator a branch tube including a first portion extending at an acute angle from the beam tube and a second portion extending from the first portion at right angles to the beam tube, a metallic bellows closed at both ends and positioned within said branch tube extensible therefrom into said beam tube, means connecting the ends of the bellows to limit longitudinal expansion thereof, a body of liquid substantially filling the bellows, and means for moving the bellows into the beam tube.

References Cited UNITED STATES PATENTS 3/1931 Drees 138-93 1/1943 Ahern 138-93 US. Cl. X.R. 250-105, 106 

